In recent years, an electronic device such as a mobile phone, a smart device (e.g., tablets, e-book reader, etc.) and an automotive navigation system is mounted with a display device with a touch panel function (i.e., a display device with touch panel, a touch panel device) having the advantage that it can provide intuitive operation and has superior durability, as one embodiment of interface.
A touch panel is a position input device which detects touch actions made by an indicator such as a finger and a stylus and identifies the coordinates of the touch position. The detection types are classified broadly into a resistive film type including an analog resistive film type and a matrix resistive film type, a capacitive type including a surface capacitive type and a projected capacitive type, an optical type including an infrared scan type and a retroreflective type, and an ultrasound waves type including a surface elastic waves type and a plate waves type. These various types have been put into practical use.
Meanwhile, in recent years, among the above-mentioned detection types, there is an increase in demand for especially a projected capacitive touch panel. The projected capacitive touch panel is configured such that, when a finger approaches, it detects changes in capacitance of electrodes near the finger as position coordinates on the touch panel, from two longitudinal and lateral rows of electrodes.
FIG. 4 is a partial cross-sectional view of one example of the projected capacitive touch panel mentioned above. A projected capacitive touch panel 51 shown in FIG. 4 has a basic structure that is manufactured by forming a sensor unit 54 and fitting the sensor unit 54 into an engagement recessed portion 55a of a housing portion 55 via an adhesive material 56 such as a double-sided adhesive tape. The sensor unit 54 includes one translucent substrate 52 and an electrode portion 53 provided on one face (i.e., a back face opposite to a front face corresponding to an operation face side) of the substrate 52. The electrode portion 53 is formed by laminating a plurality of rows of first electrodes (e.g., X electrodes) formed of transparent conductive films extending in a first direction (e.g., a lateral direction) and a plurality of rows of second electrodes (e.g., Y electrodes) formed of transparent conductive films extending in a second direction (e.g., a longitudinal direction) intersecting the first electrodes. The substrate 52 includes lead-out lines 57 which are lead out from the respective ends of the electrode portion (i.e., the first electrodes and the second electrodes) 53 and which are formed via a decorative layer 58. Furthermore, there is provided a protective layer 59 made of transparent insulating film and formed so as to entirely cover the electrode portion 53 and the lead-out lines 57 of the sensor unit 54. A display device 60 such as a liquid crystal display is adhesively fixed via an adhesive material 61 such as a transparent adhesive tape at a position opposed to the sensor unit 54 of the substrate 52. Such projected capacitive touch panel is disclosed in Patent Literature 1 mentioned below.
Patent Literature 1: Japanese Patent Application Publication No. 2011-90443